i dont have much experience with e46 just older ones, but i dont think theres a separate computer for those things. the on board computer is just a name for the screen and buttons that scroll through info like mileage and temperature. im too lazy to research e46 right now haha but all that and the instrument cluster should run off signals through the main ECU. it could be the instrument cluster itself is messed up which is pretty common/cheap/easy to fix. it should be a simple fix, even if it isnt the cluster i cant imagine anything crazy or expensive that would cause those things to not work.

take all that with a grain of salt because i have not owned or worked on an e46 ever in my life. driven my friends sick 330 zhp 6 speed all the time though!

any reason you chose an e46 328 out of all models?